[go: up one dir, main page]

snafu-derive 0.8.0

An ergonomic error handling library
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103

use quote::quote;
use syn::{spanned::Spanned, Item, ItemFn, ReturnType, Signature};

pub fn body(
    _attr: proc_macro::TokenStream,
    item: proc_macro::TokenStream,
) -> syn::Result<proc_macro2::TokenStream> {
    let item = syn::parse::<Item>(item)?;

    let f = match item {
        Item::Fn(f) => f,
        _ => {
            return Err(syn::Error::new(
                item.span(),
                "`#[snafu::report]` may only be used on functions",
            ))
        }
    };

    let ItemFn {
        attrs,
        vis,
        sig,
        block,
    } = f;

    let Signature {
        constness,
        asyncness,
        unsafety,
        abi,
        fn_token,
        ident,
        generics,
        paren_token: _,
        inputs,
        variadic,
        output,
    } = sig;

    let output_ty = match output {
        ReturnType::Default => quote! { () },
        ReturnType::Type(_, ty) => quote! { #ty },
    };

    let error_ty = quote! { <#output_ty as ::snafu::__InternalExtractErrorType>::Err };

    let output = if cfg!(feature = "rust_1_61") {
        quote! { -> ::snafu::Report<#error_ty> }
    } else {
        quote! { -> ::core::result::Result<(), ::snafu::Report<#error_ty>> }
    };

    #[allow(clippy::collapsible_else_if)]
    let block = if asyncness.is_some() {
        if cfg!(feature = "rust_1_61") {
            quote! {
                {
                    let __snafu_body = async #block;
                    <::snafu::Report<_> as ::core::convert::From<_>>::from(__snafu_body.await)
                }
            }
        } else {
            quote! {
                {
                    let __snafu_body = async #block;
                    ::core::result::Result::map_err(__snafu_body.await, ::snafu::Report::from_error)
                }
            }
        }
    } else {
        if cfg!(feature = "rust_1_61") {
            quote! {
                {
                    let __snafu_body = || #block;
                    <::snafu::Report<_> as ::core::convert::From<_>>::from(__snafu_body())
                }
            }
        } else {
            quote! {
                {
                    let __snafu_body = || #block;
                    ::core::result::Result::map_err(__snafu_body(), ::snafu::Report::from_error)
                }
            }
        }
    };

    Ok(quote! {
        #(#attrs)*
        #vis
        #constness
        #asyncness
        #unsafety
        #abi
        #fn_token
        #ident
        #generics
        (#inputs #variadic)
        #output
        #block
    })
}